Such a longitudinal guide is known, for example, from DE-C-31 43 431. However, equivalent longitudinal guides are also taught by DE-OS 25 45 763 or DE-AS 24 51 262. The longitudinal guides specified therein are manufactured either of steel sheet metal, whereby the steel grades are those commonly used in the automobile industry, or they are made of extruded light metal, preferably aluminum. The latter construction has become more prominent during the last few years. The production of tracks made of aluminum satisfies the need of the automobile industry to save weight in vehicles. The market share for tracks for longitudinal guides made of steel has dropped during the last few years, while the market share for aluminum rails has increased during that time. This is due, in particular, to the lighter weight of an aluminum track of equivalent strength as compared to a steel track.
A longitudinal guide is prevented from pulling out if the safety belts are mounted to the seat itself, that is, belt traction forces due to an accident are transferred by means of the tracks of the longitudinal guide that is interconnected with the floor group of the motor vehicle. Longitudinal guides are considered pull=out proof if there is no risk that the longitudinal guide will tear away or tear open in a zipper like manner in the event of high acceleration forces due to an accident.
The previously known longitudinal guide according to the previously mentioned DE-C-31 43 431 consists of an inner, embraced track and an outer embracing track. The inner track exhibits outward spring action, while the outer track exhibits inward spring action. These preloaded forces oppose each other in the area of the guiding means, and the guiding means are kept in position by means of the preload forces.